In all areas of the outer continental shelf and slope, female 

 populations showed slightly higher proportions of old ( > 4 yr) in- 

 dividuals than male populations. 



Sex ratio. — The overall proportion of Pacific cod females was 

 0.51 (Table 44). With the exception of subarea 4S, females were 

 more abundant than males in all regions of the study area. Fe- 

 males were also more abundant among all age groups, except age 

 2yr. 



Length-weight relationship. — A total of 650 individuals from 

 the Pacific cod populations in otolith areas B and D were 

 measured for fork length and weight (Table 45, Fig. 56). The 

 overall observed relationship was W = 0.0072 Z,'-" 25 . Statistically 



Table 44. — Proportions of females in the estimated population of Pacific 

 cod by age group and geographical area, 1976 Bering Sea spring trawl 

 survey.' 









Age group (yr) 









Subarea 1 



1 



2 



3 



4 



5 



6 



combined 









p 



irtion of females 







Inner shelf 













4S 

 1 



0.32 

 0.61 



— 



— 



— 



— 



— 



0.32 

 0.61 



Outer shelf 

















and slope 

 3S 



0.37 



0.49 



0.54 



0.56 



0.39 



0.96 



0.52 



3 Slope 



1.00 



1.00 



0.75 



0.72 



0.91 



1.00 



0.74 



2 



0.58 



0.37 



0.53 



0.65 



0.65 



0.00 



0.51 



2 Slope 



0.75 



0.46 



0.52 



0.62 



0.73 



1.00 



0.55 



All subareas 

















combined 



0.51 



0.38 



0.53 



0.62 



0.59 



0.54 



0.51 



'Based upon sampled individuals for which sexes could be determin- 

 ed. Populations in subareas 3N and 4N are not included because no length- 

 frequency data were collected. 



! See Figure 3. 



significant differences were observed in all comparisons of length- 

 weight characteristics between populations. 



Both male and female populations showed differences between 

 north and south geographical regions. Over the observed size 

 range, females were 9-10% heavier at length in otolith area D than 

 in otolith area B. Up to 65 cm FL, males were also 1-58% heavier 

 at length in otolith area D, but above 65 cm FL, they were heavier 

 in otolith area B. 



In otolith area B, males were increasingly (up to about 4%) 

 heavier at length than females. In otolith area D, up to approx- 

 imately 50 cm, males were heavier at length than females; at larger 

 fork lengths, females were heavier. 



Age-length relationship and growth. — A total of 385 scale 

 samples were collected, 215 from otolith area B and 170 from 

 otolith area D. Data from the two areas were combined to create 

 more complete age-frequency tables. Compared to other demersal 

 fish species, Pacific cod showed remarkably rapid growth at all 

 ages sampled. 



Results of the growth curve fittings are summarized in Table 46 

 and Figure 57. In general, the results were poor and indicated like- 

 ly problems in the determination of ages, particularly for the 

 youngest and oldest age groups. 



Data sets including all ages did not fit the decaying exponential 

 (von Bertalanffy) model. Within the male population, apparent 

 growth was essentially linear with nearly constant growth in- 

 crements ( + 8 to +10 cm) between age groups. The female 

 population showed increasing growth increments with age, from 

 + 8.3 cm between ages 1 and 2 yr to + 16.8 cm between ages 5 

 and 6 yr. 



To compare these results with those from other studies of 

 Pacific cod, Ketchen (1964) observed L x and K values of 94.0 

 cm and 0.27/yr from populations in northern Hecate Strait, and 

 75.0 cm and 0.56/yr from the Strait of Georgia, British Columbia 

 (fitting to combined data from both sexes in each study). 



Table 45. — Length-weight relationships observed for Pacific cod during the 1976 Bering Sea spring 

 trawl survey, with testing for between-area and berween-sex differences. 





Otolith 

 area' 



Number 

 sampled 



FL 

 range 

 (cm) 



Length-weight coefficents Predicted weight- 



at-length 



Sex 



a 



b 



10 cm 



40 cm 



70 cm 

















grams - 











Males 



B 



213 



31-74 



0.0070 



3.1213 



9.2 



697.0 



3998.1 





D 



60 



32-90 



0.0198 



2.8693 



14.6 



780.8 



3889.4 





Both areas 



















combined 



273 



31-90 



0.0079 



3.0893 



9.7 



706.9 



3982.7 



Females 



B 



253 



32-81 



0.0074 



3.0984 



9.2 



681.2 



3857.8 





D 



124 



28-107 



0.0078 



3.1081 



10.0 



743.9 



4235.8 





Both areas 



















combined 



377 



28-107 



0.0065 



3.1412 



8.9 



695.2 



4032.2 



Overall 





650 



28-107 



0.0072 



3.1125 



9.3 



701.4 



4003.9 



Analysis 



of covariance 



























Tests for differences 2 











Slope (b) 





Common means 





df 





F ratio 



df 





F ratio 



Males between areas B and D 



1:269 





6.32* 



— 





_ 



Females between areas 



B and D 



1:373 





0.19 



1:374 





33.3** 



Between 



sexes in area 



B 



1:462 





0.17 



1:463 





4.77* 



Between 



sexes in area \ 



D 



1:180 





4.97* 



- 





- 



'See Figure 4. 

 >* = P <0.05, 



= P ==0.01. 



79 



